Abstract

We demonstrate a compact, ultrahigh speed spectral-domain optical coherence microscopy (SD-OCM) system for multiscale imaging of specimens at 840 nm. Using a high speed 512-pixel line scan camera, an imaging speed of 210,000 A-scans per second was demonstrated. Interchangeable water immersion objectives with magnifications of 10×, 20×, and 40× provided co-registered en face cellular-resolution imaging over several size scales. Volumetric OCM data sets and en face OCM images were demonstrated on both normal and pathological human colon and kidney specimens ex vivo with an axial resolution of ~4.2 µm, and transverse resolutions of ~2.9 µm (10×), ~1.7 µm (20×), and ~1.1 µm (40×) in tissue. In addition, en face OCM images acquired with high numerical aperture over an extended field-of-view (FOV) were demonstrated using image mosaicking. Comparison between en face OCM images among different transverse and axial resolutions was demonstrated, which promises to help the design and evaluation of imaging performance of Fourier domain OCM systems at different resolution regimes.

(a) Spectrum of the light source measured using an optical spectrum analyzer. (b) Interference signal before (blue line) and after (black dashed line) spectral shaping using Hamming window. (c) Axial point spread function in air before (blue) and after (black dashed line) spectral shaping. Sensitivity roll-off of the spectrometer in air (d) before and (e) after spectral shaping.

En face OCM images showing morphology of the crypt structure in normal human colon as a function of focus position beneath the tissue surface. The en face images are acquired by fixing the delay length but gradually moving the focus position deeper into the tissue. Scale bars: 100 µm.